Drafting protractor



Feb- 11, 1969 H. R. ZARLING 3,426,434

DRAFTINC' PROTRACTOR Filed Nov. 5, 1967 Illy'llsTlIl 1N VENTO/. Hari/e] R. Z arl/'Iy United States Patent O 10 Claims ABSTRACT F THE DISCLOSURE A drafting protractor for use by draftsmen, architects, carpenters, engineers and others, formed of two main parts, a xed main frame and a movable frame pivoted on the ixed main frame. The xed main frame has two main arms at right angles to each other and a pointer arm extending outwardly between the two main arms. The movable frame has a graduate arcuate scale imprinted near its outer edge to which the end of the pointer arm points, so that any angle may be set or measured by merely turning the movable member on its pivot until the pointer arm points to the desired angle on the scale. A locking member is provided for locking the parts in any angular position, and the movable member has two guide slots at forty-tive degree angle separation into which a pencil may be inserted to draw a line at any set angle.

SUMMARY OF INVENTION The invention relates to a drafting protractor usable by engineers, inventors, architects, carpenters, surveyors, and the like, having a main frame with normally disposed arms. A pointer blade attached to the joining portions of the arms bisects the angle between the arms. Located below the pointer blade and between the arms is a movable member having a at body. A pivot in the area of the joining portions of the arms and blade pivotally connects the body to the frame. The body has an arcuate slot spaced from the pivot means with a radius extended from the pivot. Concentric with the slot is a graduated scale located adjacent the outer end of the pointer blade whereby the pivotal movement of the movable member relative to the frame is measured. A releasable lock screw mounted on the pointer blade and extended through the slot is operable to hold the movable member in a fixed position relative to the frame.

In the drawing:

FIGURE l is a plan view of the entire drafting instrument.

FIGURE 2 is a sectional View taken on plane 2-2 of FIGURE 1.

FIGURE 3 is a sectional view taken on plane 3-3 of FIGURE 1.

In connection with the work of a draftsman, engineer, architect and other similar occupations, it is important to have a protractor which can be set to any desired angle with a high degree of accuracy. In addition, it is preferably made of transparent material, such as clear plastic, and should be relatively inexpensive. Further, its ruling or drawing edges should be easily accessible and convenient in use. The present invention provides such a protractor.

In order to understand clearly the nature of the invention, and the best means for carrying it out, reference may be had to the drawings, in which like numerals denote similar parts throughout the several views.

As shown, there is a main frame or base generally indicated at 10, with a lower frame arm 12 integral with an upright frame arm 14 being joined at right angles at their junction 16. The outer edge margins 18 of the main frame arms are beveled as seen in FIGURES l and 2, and measuring scales 20 are imprinted or otherwise car- 3,426,434 Patented Feb. 11, 1969 ice ried on the edge margins. The inner edge margins 22 of the main frame arms are also beveled as seen in FIG- URES 1 and 2, `and may be slightly cut away from locations 24 to 26 as seen best in FIGURE 1.

It is also seen from FIGURE 2, that a recess 28 is formed on the underside of each of the main frame arms along their entire lengths, to receive the movable ruling and measuring member 30. This member 30, like the main frame member, is also formed of clear transparent plastic or similar material. A pointer blade 32 is integral with the main frame arms and extends outwardly at a 45 degree angle between them from their junction, and from FIGURE 1 it is seen that a pivot pin 34 extends through the pointer blade 32 and the underlying portion of the movable ruling and measuring member 30 so that the member 30 is movable about this pivot 34.

An arcuate scale 36, graduated in degrees is imprinted or otherwise carried on the portion 38 of the movable member 30, and the outer end 40 of the pointer arm 32 traverses the arcuate scale 36, being provided with a Vernier scale at its end for accurate measurement of angles on the scale 36. In order to hold the parts frictionally at any particular angle, a guide slot 44 which is also arcuate, is formed through the movable member 30, and a stop lock member 46 extends through the slot 44 and the overlying portion of the pointer arm 32, to hold the parts in any angle position desired until released. For this purpose, the lock member 46 may have a base 48 with an upwardly projecting riser screw 50 which may be somewhat squared olf so that as it rides in the slot 44 it will not turn around. A lock nut 52 is threaded onto the threaded upper end of the screw 50, and may be loosened or tightened as needed, to permit movement of the movable member 30 to any desired angle and then tightened to hold it at that angle. While t-he lock nut 52 is shown rounded, it may also be of any other shape to make it easy to turn it with the lingers, or may have a slot to receive a screw driver to turn it.

In order to rule lines the movable member 30 has two ruling and guide slots 60 and 62 which are formed through its upper and lower margins 64 and 66, and they are also provided with graduated scales 68 to provide easy measurement of the length of line being drawn. The scales 68 are imprinted along both edges of each guide slot 60 and 62, only one set of scales being shown for clarity, but both guide slots 60 and 62 having them. Thus, a pencil may be inserted in either guide slot and moved along either edge as convenient for making a line at any angle. With this instrument angles of any size may be measured, and lines drawn, throughout any angular displacement, and of great accuracy.

Although I have described a preferred embodiment of the invention in speciic terms, it is understood that various changes may be made in size, shape, materials and arrangement without departing from the spirit and scope of the invention as claimed.

I claim:

1. A drafting protractor comprising: main frame means having a first arm and a second arm xedly joined to and normally disposed with respect to the first arm, and al pointer blade lixedly attached to the joining portions of said first and second arms, said blade bisecting the angle between said rst and second arms whereby the pointer blade is positioned at an angle of about 45 with respect to said lirst and second arms, movable means having a at body positioned below the pointer blade, pivot means located in the area of the joining portions of the arm and blade to pivotally connect the body with the frame means, said body having an arcuate slot spaced from the pivot means with a radius extended from the pivot means, and means mounted on the pointer blade and extended through said slot to releasably lock the movable means with respect to the frame means.

2. The drafting protractor of claim 1 wherein said movable means comprises a first marginal edge portion, a second marginal edge portion angularly spaced from said rst marginal edge portion, a hub portion for engaging said pivot means for rotation of said movable means about said pivot means, and guide slot means extended along both said rst and second marginal edge portions for receiving a marking pencil to rule a line along said guide slot means.

3. The drafting protractor of claim 2 wherein said main frame means and said movable means are both formed of clear transparent material.

4. The drafting protractor of claim 2 including graduated arcuate scale means carried on said movable means concentric with said arcuate slot, said pointer blade means being integral with said main frame means and extending outwardly intermediate the junction of said arms and with its free end pointing to said arcuate scale means as the movable means is traversed about its said pivot means, whereby said pencil receiving guide slot means are brought in to any angular position for measuring and marking lines.

5. The drafting protractor of claim 1 wherein said pivot means are located at the inner end of the pointer blade in the plane of the longitudinal axis of the pointer blade.

6. The drafting protractor of claim 1 wherein each arm has a bottom inwardly directed recess of a depth generally equal to the thickness of the movable means whereby the bottom surfaces of the arms and the bottom surface of the movable means are in the same plane.

7. The drafting protractor of claim 2 wherein said rst marginal edge portion and said second edge portion have outwardly directed portions extended beyond the end of the arms.

8. The drafting protractor of claim 1 wherein the rst arm, the second arm, and the pointer blade are formed from a single piece of material joined together at a common right angle corner portion.

9. The drafting protractor of claim 1 wherein each arm has a bottom inwardly directed recess of a depth generally equal to the thickness of the marginal edge portions of the movable means whereby the marginal edge portions angularly move into the recess of the arms.

10. The drafting protractor of claim 9 wherein when the marginal edge portions of the movable means are in engagement with an associated arm the slot in said marginal end portions is generally parallel to an outer edge of the arm.

References Cited UNITED STATES PATENTS 2,251,208 7/1941 Sigmon 33-93 2,631,376 3/1953 Callahan 33-93 2,867,906 l/1959 Lee 33-93 HARRY N. HAROIAN, Primary Examiner. 

